A conventional pharmaceutical injection device of this type comprises a main case that has a pharmaceutical syringe mounting component, a piston that is provided movably with respect to the pharmaceutical syringe mounted to the pharmaceutical syringe mounting component, a driver that drives this piston, a controller that is electrically connected to this driver, a display component that is electrically connected to this controller, and a power switch. With this configuration, a needle detector switch that detects the state of mounting of an injection needle to a pharmaceutical syringe is provided to the main case, and this needle detector switch is connected to the controller (see Patent Literature 1, for example).